1. Technical Field
The present disclosure relates generally to the field of wireless communication, and data networks. More particularly, in one exemplary embodiment, methods and apparatus for managing receive operations in a multi-antenna wireless device or system are disclosed.
2. Description of Related Technology
Power consumption is a critical factor in modern mobile device design (and in fact with respect to other types of devices as well). In the particular context of mobile devices (such as cell phones, smartphones, tablets, handhelds, etc.), reducing power consumption can offer a variety of different benefits, including without limitation enhanced user experience (through e.g., the device being more available to the user, and requiring less frequent recharging, etc.), and increased longevity and reliability of the device and its components.
However, as modern wireless interface technologies have evolved, they have generally trended toward more power consumptive designs, so as to support e.g., very high data rates, streaming high-bandwidth video or other media, more complex/intensive applications, etc. In certain of such advanced wireless technologies, multiple antennas are used to, inter alia, receive wireless signals transmitted from another device (e.g., a mobile device, or base station). The use of multiple antennas for transmission and reception is commonly referred to as “antenna diversity”, and is commonly further subdivided into “receive diversity” and “transmit diversity”. Those of ordinary skill in the related arts will readily appreciate that various other types of diversity exist and are commonly used (e.g., time diversity, frequency diversity, spatial diversity, polarization diversity, etc.).
In the exemplary context of Long Term Evolution (LTE), existing LTE user equipment (UE) utilizes an antenna diversity scheme that is statically configured and invariant. More directly, the number of antennas that are available for use does not change (i.e., “static”). The LTE standard (and hence any compliant transmitting device such as a base station) assumes that the UE is configured with at least two (2) receive “chains” (as used hereinafter, the term “chain” refers to one or more chained processing elements and/or logic). While diversity implementations can provide higher data rate, diversity also consumes more power than using a single receive chain.
Unfortunately, receiver diversity may not be necessary under certain conditions, such as for example: (i) when receiving relatively low data rate signaling (e.g., a physical downlink control channel (PDCCH) or paging message(s) when radio conditions are good), (ii) when receiving a so-called “rank one (1)” transmission, etc. As a brief aside, the term “rank” formally refers to the mathematical rank (i.e., the number of linearly independent eigen-vectors) of a channel matrix that represents the communication channels (h) between each pair of transmit (columns) and receive antennas (rows). However, as used within common parlance (e.g., within the LTE standard), “rank” refers to the number of spatial layers transmitted from transmitter. For example, a rank one (1) transmission represents the usage scenario where each of the transmitters is transmitting essentially the same data or a linear transformation of the same data. In the exemplary case of LTE, an eNB that is transmitting a rank one (1) transmission is sending only one layer of information. More generally, receiver diversity is unnecessary in any scenario where the increase in data rate or the increase in reliability provided by diversity operation does not justify its “cost” (e.g., power consumption, processing complexity, etc.).
Therefore, there is a need for, inter alia, an “adaptive” mechanism to selectively or intelligently enable/disable more power consumptive operational modes (such as receiver diversity modes in an exemplary LTE networks) in order to, inter alia, reduce power consumption in the mobile device, ideally without compromising mobile device performance (and hence user experience).